title: Effect of labor on maternal cerebral blood flow velocity.
abstract: OBJECTIVE
  Our purpose was to determine the effect of contractions and second-stage pushing on cerebral blood flow velocity as an indirect assessment of cerebral hemodynamic changes during labor and delivery.
  
  
  METHODS
  A prospective cohort of 15 normotensive patients in early labor had maternal middle cerebral blood flow velocity assessed continuously with transcranial Doppler ultrasonography. Assessment was performed during the peak of a contraction, during the trough of a contraction, and with pushing in the second stage. We assessed systolic, diastolic, mean cerebral blood flow velocity (in centimeters per second), and pulsatility index over four contractions. We used analysis of variance to compare velocities at these three stages.
  
  
  RESULTS
  Mean maternal cerebral blood flow velocity fell significantly (61.2 +/- 6.4, 50 +/- 10.2, 52.2 +/- 6.5 cm/sec) (p < 0.008). Pulse rate rose significantly by 16 beats/min (p < 0.0001), but no significant change in blood pressure occurred in patients during second-stage labor when pushing.
  
  
  CONCLUSIONS
  Middle cerebral vessels vasodilated during the peak of contractions and second-stage pushing as assessed by transcranial Doppler ultrasonography. Pushing in the second stage with the Valsalva maneuver does not expose the patient to a greater risk for middle cerebral vasospasm than contractions developing in the first stage.
authors.affiliation: University of British Columbia, Department of Obstetrics and Gynaecology, Canada.
authors.forename: K P
authors.initials: KP
authors.lastname: Williams
authors.forename: F
authors.initials: F
authors.lastname: Galerneau
authors.forename: S
authors.initials: S
authors.lastname: Wilson
mesh_terms: D000704:Analysis of Variance; D001794:Blood Pressure / Q000502:physiology; D001921:Brain / Q000098:blood supply*; D002536:Cerebral Arteries / Q000000981:diagnostic imaging / Q000502:physiology*; D015331:Cohort Studies; D004453:Echoencephalography; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D007743:Labor, Obstetric / Q000502:physiology*; D011247:Pregnancy / Q000502:physiology*; D011446:Prospective Studies; D012039:Regional Blood Flow / Q000502:physiology; D018608:Ultrasonography, Doppler; D014590:Uterine Contraction / Q000502:physiology; D014636:Valsalva Maneuver